The art of propelling objects through tubes is as old as the primitive blow gun which finds modern usage in the bane of all school classrooms; the pea shooter.
Many attempts have been made to transport freight and people through tubes using a quantity of air acting upon a vehicle. Movement of the vehicle has been no problem in the "pea shooter" systems but their nemesis has been in dealing with the huge quantities of system air rushing from the downstream portal or in diverting the system air around the mid point system stations. The difficulty is that such huge quantities of system air must be separated from passengers exiting the vehicle or even with freight vehicles, the system air must be separated from the workers loading and unloading the vehicle.
Pitts, U.S. Pat. No. 384,333 (1888) was an early attempt to move passengers using a wheeled vehicle which mounted a fan which was driven by the system air and in turn was geared to the wheels of the vehicle. The system air was diverted around the loading and unloading stations; the vehicle acted as a gate valve and passengers loaded through a close fitting opening in the tube which registered with the vehicle doors.
Knox, U.S. Pat. No. 1,813,625 (1931) used diversion valves at the stations.
James, U.S. Pat. No. 3,352,512 (1967) shows novel orange peel valves at the stations.
Ottersen, U.S. Pat. No. 3,711,038 (1973) eliminates the rushing air problem by simply shutting down the entire system when the vehicle reaches the station.
Carstens, U.S. Pat. No. 3,797,405 (1974) diverts the air at each station in the system shown in FIGS. 1 and 7 and uses chimneys adjacent the dead end stations as shown in FIGS. 11 and 12.
Carstens, unlike the present system, is a "booster system"; i.e., the air nozzles inject a small volume of air at high speed at each pumping station which strikes the larger body of slower moving air and boosts its speed.